Method and apparatus for stabilizing formations



V. N. SWIFT Nov. 21, 1967 METHOD AND APPARATUS FOR STABILIZING FORMATIONS Filed Aug. 4. 1964 IN VEN TOR.

Arme/vEV.

United States Patent 3,353,599 METHOD AND APPARATUS FOR STABILIZHNG FORMATIONS Virgil N. Swift, Galliano, La, assignor to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 4, 1964, Ser. No. 387,345 17 Claims. (Cl. 166-15) This invention relates to a method and an apparatus for preventing the movement around and into a well bore of individual particles comprising an unconsolidated rock formation.

Many underground rock formations are unconsolidated or so poorly consolidated that they disintegrate under the forces exerted upon them by the weight of the overbearing rock and by the fiow of formation fluids into a well bore penetrating the formation. Such rock formations are hereinafter referred to generally as unconsolidated formations. It has been found that, when fluids flow from an unconsolidated formation into a well bore, the displacement of formation particles into the well bore permits the movement of additional particles farther back in the formation and results in plugging of the well bore and of the formation flow channels around the well bore. To prevent the rearrangement of the formation particles under the forces of fluid flow and overburden pressure, it is necessary to prevent substantially the movement of formation particles into the Well bore. It is possible to assure the substantially complete prevention of the movement of formation particles around or into the well bore by providing mechanical support for the formation particles around the well bore. Such mechanical support should impart to the formation particles a force directed outwardly from the well bore whereby the formation particles are retained essentially undisturbed during the production of formation fluids.

Various methods have been suggested for alleviating the problems involved in producing fluids from an unconsolidated formation, one such method, a slotted or otherwise perforated pipe or liner is centralized in the well bore and the annulus between the liner and the wall of the well bore is packed with gravel. The gravel pack is used to filter the formation particles from the produced fluids to prevent their entry into the liner. However, one disadvantage of such a method is that placement of the gravel pack and the liner in the well bore greatly reduces the diameter of the well here extending through the unconsolidated formation. Furthermore, in unconsolidated formations located in the upper intervals of a well bore penetrating a number of oil bearing formations where it is desirable to produce simultaneously from more than one of such formations, the methods presently available for gravel packing a dually completed well bore are cumbersome and expensive and require a complicated and time consuming fishing operation for retrieval of the gravel pack apparatus if it is necessary to treat or work over the lower producing formations. A further disadvantage of such a well completion method arises from the difficulty of obtaining an effective gravel pack in the annular space between the centralized liner and the wall of the well bore- It has been suggested that a well bore extending through a number of oil bearing formations can be completed to permit production from more than one of such formations simultaneously by setting a perforated casing through the upper unconsolidated formations and injecting an aggregate of graded gravel through the perforations behind the casing to prevent the flow of formation particles into the casing. That well completion method does not employ a screen to keep the gravel in place, but rather employs the larger gravel particles to bridge the casing perfora- 3,353,599 Patented Nov. 21, 196? tions and prevent movement of the gravel into the Well bore. In some instances this bridging action is not accomplished at all and in other instances, although the gravel initially bridges in the casing perforations, it is later disrupted by the flow of fluids, especially formation water, through the perforations, thereby permitting entry of gravel and formation particles into the well bore.

It is an object of this invention to provide a more effective method and apparatus for completing a well bore extending through an unconsolidated formation to prevent movement of the formation particles around and into the well bore. It is a further object of this invention to provide a more reliable method and apparatus for completing a well bore through unconsolidated formations located in upper intervals of a well bore penetrating a number of oil bearing formations.

This invention resides in a method and apparatus for preventing the movement of formation particles in an unconsolidated rock formation around and into the well bore by providing mechanical support to the formation particles and continuously exerting a force outwardly from the well bore upon the formation particles while maintaining the internal diameter of the fluid passage extending through the well bore substantially the same as the internal diameter of the casing in the well bore.

An embodiment of this invention is described herein with reference to the accompanying drawings in which FIGURES 1 through 4 are elevational views, partially in cross section, of the well bore apparatus and the surrounding unconsolidated formation during various stages of the process of this invention.

FIGURE 1 is a view of the well bore during the packing of the formation with gravel.

FIGURE 2 is a view of the well bore during the removal of excess gravel.

FIGURE 3 depicts an expansible permeable liner mounted on a setting tool and inserted in the well bore adjacent the unconsolidated formation.

FIGURE 4 shows the expanded permeable liner set in the well bore in forcible engagement with the well casing through the perforated interval of the casing adjacent thegravel-packed unconsolidated formation.

FIGURE 5 is an isometric view, partially in cross section, of one type of expansible permeable liner suitable for use with the method of this invention.

According to the method of this invention, gravel is squeezed under pressure into the unconsolidated formation through perforations extending through the wall of casing cemented through the formation and, thereafter, a thin-walled permeable liner is expanded into forcible engagement with the wall of the casing extending through the interval of the casing perforations. As used herein, the term gravel refers to an aggregate of graded particulate solids which may consist of sand, glass or plastic beads, or a mixture of such natural and manufactured materials. For the process of this invention, the gravel preferably is essentially spherical and ranges in diameter from 0.0331 in. to 0.0035 in., which corresponds to a range of from 20 to mesh, U. S. Standard Sieve Series.

The procedural steps involved in the application of this method can be explained with reference to FIGURES 1 through 4 of the accompanying drawings. FIGURE 1 shows a well bore '10 penetrating an unconsolidated formation 12. A string of steel casing 14 extends through formation 12 and is secured to the wall of well bore 10 by a cement sheath 18. A retrievable bridge plug 16 is set in casing 14 below formation 12 to isolate formation 12 and the upper section of well bore 10 from the lower section of well bore 10 extending into deeper formations.

A plurality of perforations 20 are cut through the wall of casing 14 and cement sheath 18 and extend into formation 12. Perforations 20 may be formed by a suitable means (not shown in the drawing) such as an hydraulic abrasive jet perforator, a bullet gun perfo'rator, a shaped charge perforator, or a mechanical knife perforator After casing 14 is perforated, a string of oil well tubing, hereinafter referred to as the gravel supply tubing 22, is run in casing 14 to a depth just above the uppermost of per forations 20. A packer 24, such as a full-opening hook wall type packer, is run in on the bottom of tubing 22 and set in the annulus 26 between gravel supply tubing 22 and casing 14 near the lower end of tubing 22.

After packer 24 is set in annulus 26, a carrier liquid containing gravel is injected through tubing 22 into casing 14. A suitable carrier liquid can consist of fresh water, brine, diesel oil, lease oil, or any other liquid which will not, in a particular formation, impair significantly the formation permeability around the well bore. Ordinarily, the density of the carrier liquid is adjusted so that the hydrostatic pressure exerted by a column of carrier liquid in the well bore slightly exceeds the forces tending to drive fluids and formation particles from the formation. The viscosity of the carrier liquid is adjusted to enable the liquid to transport a concentration of 0.5 to 6.0 pounds of gravel per gallon of liquid without excessive deposition of gravel in the well bore.

As the carrier liquid is forced through perforations 20 into formation 12, the gravel is squeezed behind cement sheath 18 to form a gravel pack 28 around well bore contiguous to the formation particles while the carrier liquid bleeds off into formation 12 behind gravel pack 28. Additional gravel is squeezed through perforations 20 by increasing slightly the injection rate of the carrier liquid. In some instances, it is undesirable to cause pressure parting of the formation, and the injection of carrier liquid is terminated when the increase in injection pressure accompanying an increase in rate would raise the bottom hole injection pressure to the pressure required to part formation 12. Experience has shown that many underground rock formations part or fracture when the injection pressure in the well bore is equal to approximately 0.7 psi per foot of depth. In other instances, it is desirable to employ higher injection pressures to create gravel packed fractures that extend into the formation beyond the main body of the gravel pack around the well bore. In those cases, the gravel squeezing operation is terminated when the injection pressures become excessive for the equipment used.

After gravel pack 28 is placed around well bore 10, packer 24 is disengaged and removed from casing 14 with gravel supply tubing 22. Next, as shown in FIGURE 2, a string of oil field tubing, hereinafter referred to as a wash pipe 30, is inserted in casing 14 and a wash liquid, such as brine, is injected downwardly through annulus 26 to displace excess gravel from the bottom of casing 14 upwardly to the surface through wash pipe 30. During the washing operation, the pressure in the well bore is higher than that in the formation to prevent the entry of gravel from the perforations 20 into casing 14. At all times during the application of the process of this invention prior to completion of the process and the subsequent production of formation fluids, sufficient pressure is maintained on the formation 12 by a column of fluid supported within casing 14 to prevent entry of gravel or individual particles from formation 12 into casing 14.

After casing 14 has been cleaned, an expansible permeable liner 32 is llTlOlllltBCl on a setting tool, indicated generally in FIGURE 3 by reference numeral 34, which is connected to the bottom of a string of conventional oil field tubing 36 and inserted in casing 14 adjacent perforations 20. Liner 32 and setting tool 34 are run in the well bore in the unexpanded condition in which the external diameters of liner 32 and setting tool 34 are less then the internal diameter of casing 14. Setting tool 34 is shown here merely as a diagrammatic representation to explain the liner expansion operation and is not intended as a detailed description of any particular tool suitable for use in this invention. Because the specific 4 elements of construction of any particular setting tool 34 are not a critical part of the inventive concept disclosed herein, no attempt is made to describe any or all of the various types of setting tools which would serve the purpose of this method.

As shown here for purposes of illustration, setting tool 34 comprises a rigid upper liner stop 38 connected to a set of expansible tubing slips 44 which is slidably secured around tubing 36. Upward motion of slips 44 and liner stop 38 along tubing 36 is prevented by a sleeve 42 welded to tubing 36. Liner 32 is mounted on setting tool 34 with the upper end of liner 32 adjacent the lower end of liner stop 38. Because liner stop 38 cannot move upwardly along tubing 36, the upward movement of liner 32 around tubing 36 is prevented as liner 32 and setting tool 34 are inserted into casing 14. When the unexpanded liner 32 is properly positioned in casing 14 adjacent perforations 20, slips 44 are set and engage the wall of casing 14, thereby preventing upward movement of liner stop 38 and liner 32 as the liner is expanded.

Tubing 36 extends through setting tool 34 and is closed at its lower end 46. An hydraulically operated liner expander 50 is connected to the lower end of tubing 36. After liner 32 is positioned in casing 14 and slips 44 are set therein, liner 32 is expanded into forcible engagement with the wall of casing 14 in the following manner. The lower end of tubing 36 and expander 50 are in fiuid communication such that fluid pressure exerted by a column of liquid supported in tubing 36 can be transmitted to expander 50 to increase the external diameter of expander 50 to a value just slightly less than the internal diameter of casing 14. Then tubing 36 and expander 50 are slowly raised upwardly through liner 32. Slips 44 and liner stop 38 remain fixed in position, thereby preventing upward movement of liner 32 as the liner is expanded by the upward motion of expander 50. When expander 50 has traversed the entire length of liner 32, expander 50 seats partially within liner stop 38. Slips 44 are released and disengaged from casing 14, and tubing 36 and setting tool 34 are removed from casing 14. Then retrievable bridge plug 16 is released and removed from well bore 10 on a wire line or with a retrieving tool suspended from the lower end of a tubing string. FIGURE 4 shows liner 32 expanded in casing 14 while leaving the passage extending therethrough substantially unobstructed.

Many different designs of expansible permeable liner 32 are suitable for use with the process of this invention. One condition placed upon the design of liner 32 is that the liner be thinwalled so as not to obstruct substantially the passage through casing 14 when liner 32 is expanded. For example, the wall thickness of the liner might vary from a thickness of 0.065 in. for use in 2% in. OD. casing to 0.125 in. for use in 5 /2 in. OD. and larger casing. An additional requirement is that liner 32 must be permeable to permit fluid communication between formation 12 and casing 14. Also the liner \must be adapted to prevent the entry of gravel or formation particles into the casing by exerting outwardly from casing 14 a positive restraining force upon the gravel extending through perforations 20 to prevent movement of gravel and of the contiguous formation particles. Because of the high permeability of liner 32, little force is exerted upon the liner wall as the result of fluid flow from the formation. Usually, the circumference of the liner in the original expanded condition is about two percent larger than the internal circumference of the casing in which the liner is set. Therefore, when the liner is permanently deformed inside the casing, the liner is left in compressive stress which is capable of withstanding the externally applied forces tending to collapse the liner.

A specific type of liner 32 suitable for use with the process of this invention is shown in FIGURE 5. The liner represented therein comprises a fluted, thin-walled metallic tube 32 having a plurality of vertical rectangular slots 52 cut through its wall. The entire length of liner 32 is slotted except for one or two feet from each end. The ends of the liner are coated with a glass-fabric mat 54 impregnated with a sealing material such as a thermalsetting epoxy resin catalyzed to give a setting time adequate to allow placement of the liner in the desired position. The size of slots 52 is determined by the range of diameters of the particles in gravel pack 28. When liner 32 is expanded, the width of slots 52 should be small enough to prevent the entry of the smallest gravel particles into liner 32.

The plastic impregnated glass-fabric mats 54 at the ends of liner 32 are extruded between the casing and liner to provide a fluid-tight seal between liner 32 and casing 14 when the liner is expanded. Liner 32 is sufiicientiy malleable to conform substantially to the inner wall of casing 14. A casing liner similar in design to liner 32 has been described in a publication entitled Stressed Steel Liner Yields Stronger Casing Repairs, by R. P. Vincent and E. R. Jennings in the Journal of Petroleum Technology, December 1962, at page 1337. Additional information has been presented in a later publication entitled Field Results of the Stressed Steel Liner Casing Patch, by G. Kemp in the Journal of Petroleum Technology, February 1964, at page 147. Those publications describe the use of stressed steel liners coated with a plastic impregnated fabric mat to seal leaks and perforations in oil well casing. The liner described in this application for Letters Patent differs from the casing patch described in the above publications in that the liner used with the process of this invention is permeable and provides a fluid seal only at the ends of the liner.

The use of the process of this invention can be explained further by the following example. A seven inch diameter well bore is drilled to a total depth of 2350 feet and extends through an unconsolidated sandstone formation, at a depth of 1400 feet, having an average thickness of 15 feet. A string of 5 /2 inch oil well casing is run to the bottom of the well bore and cemented in place. A retrievable bridge plug is set in the casing at a depth of 1430 feet and the casing isperforated over the interval of the formation extending from a depth of 1403 to 1412 feet by a bullet perforator which forms perforations having a diameter of approximately /8 of an inch. Hydrostatic pressure is maintained on the formation by a column of brine having a density of 9.5 pounds per gallon supported in the casing. A string of 2 /2 inch oil well tubing is run in the casing to a depth of 1400 feet and a hook wall packer is set in the casing around the tubing at a depth of 1390 feet.

A carrier liquid comprising diesel oil containing 1 /2 pounds of gravel per gallon of diesel oil is injected through the tubing into the bottom of the casing at an initial rate of 1.0 bbl./ min. The gravel entrained in the carrier liquid is graded, each particle of gravel having a diameter within the range of from 0.0331 to 0.0165 inch; this is equivalent to a range of from 20 to 40 mesh, US. Standard Sieve Series. The pressure required to part this formation is equal to approximately 990 psi. and, when the bottom hole injection pressure on the carrier liquid reaches a value of 900 p.s.i., injection of the carrier liquid is terminated. The packing tubing and packer are then removed from the well bore and a string of wash pipe with a mule shoe joint on the bottom is inserted in the casing. Brine, having a density of9.5 pounds per gallon, is circulated downthe annulus and upwardly through the wash pipe to displace theexcess gravel from the casing.

With the casing cleaned and hydrostatic pressure maintained on the gravel pack to prevent its re-entry into the casing, a setting tool and liner are run in the well bore on a string of 2 /2 inch tubing. The liner has a Wall thickness of 0.125 inch and a length of 16 feet to assure its coverage of the entire perforated interval of the casing. A glass fabric mat impregnatedwith a thermal-setting epoxy resin is secured to either end of the liner over a distance of two feet from each end. The mat has a thickness of 0.025 inch, and the combined thickness of the liner and the glass mat results in a reduction of the inner diameter of the casing of only 0.30 inch when the liner is expanded. The intermediate section of the liner contains a number of staggered rows of rectangular slots having a width, when the liner is expanded, of approximately 0.015 inch.

After the liner and setting tool are properly positioned in the well bore, the slips at the upper end of the setting tool are set in the casing and fluid pressure is applied through the tubing to the expander in the lower end of the setting tool. The tubing and expander are drawn upwardly through the casing, thereby expanding the liner into forcible engagement with the wall of the casing. Thereafter the setting tool and tubing are removed from the well bore, and the bridge plug is retrieved on a wire line from the casing below the formation. Fluid production is commenced through the substantially unobstructed passage through the casing which permits the insertion of additional producing equipment through the unconsolidated formation to producing formations located farther down in the well bore.

This invention has the advantage of providing a permanently deformed liner set in the well bore in compression inside the casing and capable of continuously exerting a retaining force directed outwardly from the well bore upon the gravel and formation particles. Such an apparatus is necessary for the permanent prevention of sanding or plugging of the well bore. This process and apparatus facilitate the simultaneous production of fluids from an unconsolidated formation and from formations located lower in the well bore. Another advantage of this invention is that it eliminates the need for placing a gravel pack in the annulus between the wall of the well bore and a centralized screen or liner. Experience has shown that the placing of an effective gravel pack around such centralized liners is difiicult and often does not prevent plugging of the flow passage through the well bore.

The procedural steps described in the preceding specification are merely representative of suitable means, and are not presented as the exclusive means, for performing this invention. Many variations in the specific technique employed are possible and within the purview of this invention as long as the fundamental steps of this process are performed. Those fundamental steps comprise providing mechanical support to the individual formation particles by a gravel pack around the well bore and exerting an outwardly directed restraining force upon the gravel pack and formation particles sufiicient to substantially prevent motion of said particles around or into the well bore while maintaining the passage through the well bore substantially unobstructed.

I claim:

1. In a well bore penetrating an unconsolidated subterranean rock formation and containing a string of easing extending through said formation, said casing secured to the wall of the well bore by a sheath of cement and in fluid communication with the formation through a plurality of perforations extending through the wall of the casing and the cement sheath, a method to prevent the movement of formation particles in the formation and into the casing comprising squeezing a body of graded gravel into the formation behind the casing, and setting and expanding a thin-walled expansible permeable liner in forcible engagement with the wall of the casing whereby the internal diameter of the casing and liner is maintained substantially equal to the original internal diameter of the casing and whereby a force is exerted outwardly from the well bore upon the graded gravel at the perforations to substantially prevent movement of the gravel.

2. In a method for completing a well bore penetrating an unconsolidated subterranean rock formation comprising setting in the well bore through said formation a string of casing, securing said casing to the wall of the Well bore with a cement sheath, creating a plurality of perforations extending through the wall of the casing and the cement sheath into said formation, squeezing graded gravel through the perforations into the formation behind the casing and cement sheath, and washing excess gravel from the interior of the casing, the improvement comprising inserting in the casing adjacent the perforations a thinwalled expansible permeable liner, permanently deforming the liner into forcible engagement with the wall of the casing, thereby maintaining a substantially unobstructed passage through the casing, said liner contacting the gravel at the perforations to substantially prevent movement of the gravel.

3. A method according to claim 2 wherein the liner comprises a fluted metallic tubular liner having a plurality of slots extending through the wall of said liner.

4. A method according to claim 2 wherein the liner extends within the casing from a point substantially below the lowest perforation to a point substantially above the highest perforation and the external surfaces of the liner extending above the highest perforation and below the lowest perforation are coated with a deformable impermeable material adapted to form a fluid-tight seal between the casing and the liner.

5. A method according to claim 4 wherein the deformable material forming the fluid-tight seal between the casing and the liner comprises a glass fabric mat impregnated with a thermally setting epoxy resin.

6. A method according to claim 2 wherein the expanded liner has a plurality of longitudinally oriented rectangular slots having a width slightly less than the diameter of the smallest particles contained in the gravel.

7. A method for completing a well bore penetrating an unconsolidated subsurface rock formation comprising setting in the well bore from the surface through the formation a string of casing secured to the wall of the well bore by a cement sheath, creating a number of perforations extending through the casing and cement into the formation, running a string of gravel supply tubing in the well bore from the surface to a level slightly above the uppermost perforation, setting a packer in the casing around the tubing near the lower end of the tubing above the uppermost perforations, injecting down the tubing a carrier liquid containing graded gravel, gradually increasing the injection rate of the carrier liquid to'squeeze the gravel through the perforations into forcible engagement with particles of the formation, continually injecting carrier liquid and gravel to squeeze additional gravel through the perforations, releasing the packer and removing the packer and tubing from the well bore while maintaining fluid pressure on the gravel, running a string of wash pipe into the casing and injecting a wash liquid down the annulus between the wash pipe and the casing to displace the excess gravel upwardly through the wash pipe, thereafter, maintaining fluid pressure on the gravel while removing the wash pipe from the casing, setting in the well bore a thin-walled expansible permeable liner through an interval extending over the perforated interval of the casing, and permanently deforming the liner into forcible engagement with the wall of the casing to maintain the passage through the casing substantially equal to the internal diameter of the casing while exerting a force on the gravel to substantially prevent movement of the gravel.

8. In a method for completing a well bore penetrating an unconsolidated subterranean rock formation comprising setting a string of casing in the well bore through the formation, securing the casing to the Wall of the well bore with a cement sheath, creating a plurality of perforations extending through the casing and the cement sheath into the formation, injecting a graded aggregate of gravel through the perforations into forcible engagement with formation particles behind the casing and cement sheath, and washing excess gravel from the interior of the easing, the improvement comprising inserting in the casing a string of setting pipe having attached at its lower end an expansible permeable liner and a setting tool, setting the liner and tool in the casing opposite the formation adjacent the perforations, thereafter expanding the liner outwardly to permanently deform the liner into compression with the wall of the casing, thereby imparting support at the perforations to the gravel to substantially prevent movement of the gravel and of formation particles contiguous to the gravel, removing the setting pipe and setting tool from the well bore, thereby leaving a substantially unobstructed passage extending through the casing from the formation to the surface.

9. In a well bore penetrating an unconsolidated subterranean rock formation and containing a string of casing extending to a depth below the bottom of said formation, said casing being secured to the wall of the well bore by a sheath of cement set around the casing and in fluid communication with the formation through a plurality of perforations extending through the wall of the casing and the cement sheath into the formation, a method for preventing the movement of formation particles in the formation and into the well bore comprising injecting into the well bore a carrier liquid mixed with graded gravel, gradually increasing the injection rate of said carrier liquid to squeeze the gravel through the perforations and into the formation in forcible engagement with formation particles immediately adjacent said gravel, continuing the injection of gravel and carrier liquid until the pressure required to force additional gravel into the formation is slightly less than the pressure necessary to part the formation, thereafter introducing into the casing a wash liquid to displace the carrier liquid and excess gravel from the casing, inserting into the casing an expansible permeable liner extending from a depth substantially below the lowest perforation to a depth substantially above the highest perforation in the casing, expanding said liner into compression with the wall of the casing and the gravel at the perforations, thereby exerting upon the gravel a restraining force suflicient to prevent substantially movement of the gravel while maintaining a substantially unobstructed passage in the well bore through the formation, and thereafter producing formation fluids from the formation through the gravel and liner and upwardly through the casing.

10. In a well bore penetrating an unconsolidated subterranean rock formation and containing a string of casing extending to a depth below the bottom of said formation, said casing being secured to the wall of the well bore by a sheath of cement set around the casing and in fluid communication with the formation through a plurality of perforations extending through the wall of the casing and the cement sheath into the formation, a method for preventing the movement of formation particles in the formation and into the well bore comprising injecting into the well bore a carrier liquid mixed with graded gravel, gradually increasing the injection rate of said carrier liquid to squeeze the gravel through the perforations and into the formation in forcible engagement with formation particles immediately adjacent said gravel, continuing the injection of gravel and carrier liquid at gradually increasing rates until the formation is parted by the force of the injection pressure, thereby forming gravel packed fractures extending into the formation from a main body of gravel around the well bore, thereafter introducing into the casing a wash liquid to displace the carrier liquid and excess gravel from the casing, inserting into the casing an expansible permeable liner extending from a depth substantially below the lowest perforation to a depth substantially above the highest perforation in the casing, permanently deforming said liner into compression with the wall of the casing and the gravel at the perforations, thereby exerting upon the gravel a restraining force suflicient to prevent substantially movement of the gravel while maintaining a substantially unobstructed passage in the well bore through the formation, and thereafter producing formation fluids from the formation through the gravel and liner and upwardly through the casing.

11.'In a well apparatus for completing a well bore penetrating an unconsolidated subterranean rock formation comprising a string of easing cemented in the well bore through said formation and having a plurality of perforations extending through the cement and into the formation, and a gravel pack maintained behind the easing and'cement in forcible engagement with particles of the formation, the improvement comprising a thin walled expansible permeable liner permanently deformed into forcible engagement with the Wall of the casing over the perforated interval of the casing whereby said liner is supportedtherein by compressive stresses sufiicient to exert a' force upon the gravel at the perforations to substantially prevent movement of the gravel, said liner having an inner diameter in its expanded condition substantially as large as the inner diameter of the casing.

12. An apparatus according to claim 11 wherein the liner comprises a fluted tubular metallic liner containing a plurality of slots, said slots having a width preventing flow of gravel into the well.

13. An apparatus according to claim 11 wherein the liner has means secured to the upper and lower ends thereof above and below the perforated interval of the casing adapted to provide a fluid-tight seal between the casing adapted to provide a fluid-tight seal between the casing and the liner.

14. An apparatus according to claim 13 wherein the means adapted to provide a fluid seal between the liner and the casing comprises a glass fabric mat secured to the liner and impregnated with a thermally setting epoxy resin.

15. A well apparatus for completing a well bore penetrating an unconsolidated subterranean rock formation comprising a string of steel casing extending through the formation and secured to the wall of the well bore by a cement sheath, said casing having a plurality of perforations extending through the casing and cement sheath into the formation, a compacted body of gravel sustained in forcible engagement with the formation around the W611 bore over the interval of the perforations, and a thinwalled expansible permeable liner permanently deformed into compression with the wall of the casing over the perforated interval, said liner exerting a force to prevent entry of the gravel into the casing while maintaining the internal diameter through the well apparatus substantially equal to the original internal diameter of the casing.

16. A method according to claim 15 wherein the liner comprises a slotted metallic tube having means secured to the outer surfaces of the ends thereof to provide a fluid-tight seal between the casing and the liner.

17. A method according to claim 16 wherein the casing comprises a conventional oil well casing having a nominal diameter of 5 /2 inches, the liner comprises a corrugated steel tube having a wall thickness of 0.125 inch and an actual outside diameter before corrugation of five inches, and the means adapted to provide a fluid-tight seal between the liner and casing comprises a glass fabric mat impregnated with a thermally setting epoxy resin and having a thickness of 0.025 inch.

References Cited UNITED STATES PATENTS 2,652,117 9/1953 Arendt et al. 16651 2,685,340 8/1954 Shea et al. 16619 2,812,025 11/1957 Teaque et al 166207 3,067,801 12/1962 SOrtol' 166-207 3,179,168 4/1965 Vincent 166--46 3,216,497 11/1965 Howard et al. 166-51 JAMES A. LEPPINK, Primary Examiner. 

1. IN A WELL BORE PENETRATING AN UNCONSOLIDATED SUBTERRANEAN ROCK FORMATION AND CONTAINING A STRING OF CASING EXTENDING THROUGH SAID FORMATION, SAID CASING SECURED TO THE WALL OF THE WELL BORE BY A SHEATH OF CEMENT AND IN FLUID COMMUNICATION WITH THE FORMATION THROUGH A PLURALITY OF PERFORATIONS EXTENDING THROUGH THE WALL OF THE CASING AND THE CEMENT SHEATH, A METHOD TO PREVENT THE MOVEMENT OF FORMATION PARTICLES IN THE FORMATION AND INTO THE CASING COMPRISING SQUEEZING A BODY OF GRADED GRAVEL INTO THE FORMATION BEHIND THE CASING, AND SETTING AND EXPANDING A THIN-WALLED EXPANSIBLE PERMEABLE LINER IN FORCIBLE ENGAGEMENT WITH THE WALL OF THE CASING WHEREBY THE INTERNAL DIAMETER OF THE CASING AND LINER IS MAINTAINED SUBSTANTIALLY EQUAL TO THE ORIGINAL INTERNAL DIAMETER OF THE CASING AND WHEREBY A FORCE IS EXERTED OUTWARDLY FROM THE WELL BORE UPON THE GRADED GRAVEL AT THE PERFORATIONS TO SUBSTANTIALLY PREVENT MOVEMENT OF THE GRAVEL.
 11. IN A WELL APPARATUS FOR COMPLETING A WELL BORE PENETRATING AN UNCONSOLIDATED SUBTERRANEAN ROCK FORMATION COMPRISING A STRING OF CASING CEMENTED IN THE WELL BORE THROUGH SAID FORMATION AND HAVING A PLURALITY OF PERFORATIONS EXTENDING THROUGH THE CEMENT AND INTO THE FORMATION, AND A GRAVEL PACK MAINTAINED BEHIND THE CASING AND CEMENT IN FORCIBLE ENGAGEMENT WITH PARTICLES OF THE FORMATION, THE IMPROVEMENT COMPRISING A THIN-WALLED EXPANSIBLE PERMEABLE LINER PERMANENTLY DEFORMED INTO FORCIBLE ENGAGEMENT WITH WALL OF THE CASING OVER THE PERFORATED INTERVAL OF THE CASING WHEREBY SAID LINER IS SUPPORTED THEREIN BY COMPRESSIVE STRESSES SUFFICIENT TO EXERT A FORCE UPON THE GRAVEL AT THE PERFORATIONS TO SUBSTANTIALLY PREVENT MOVEMENT OF THE GRAVEL, SAID LINER HAVING AN INNER DIAMETER IN ITS EXPANDED CONDITION SUBSTANTIALLY AS LARGE AS THE INNER DIAMETER OF THE CASING. 